Fluticasone propionate is the approved name for S-fluoromethyl 6a, 9a-difluoro-11b-hydroxy-16a-methyl-17a-propionyloxy-3-oxandrosta-1, 4-diene 17b carbothioate, a corticosteroid known to exhibit topical antiinflammatory activity and described and claimed in GB 2088877. In the treatment of asthmatic conditions it has been found to be effective to administer fluticasone propionate in the form of dry powders or aerosols containing small particles of the medicament, conventionally prepared by micronisation. Conventionally, fluticasone propionate aerosols have been administered by means of metered dose inhalers, which are designed to deliver a fixed unit dosage of medicament per actuation or "puff". However, some patients, in particular children and the elderly, have difficulty in coordinating actuation of a metered dose inhaler with inhalation, and are therefore unable to use this mode of administration effectively. Furthermore, a proportion of patients find inhalation of dry powders difficult or unpleasant. There is therefore a demand for a pharmaceutical formulation containing fluticasone propionate in a form suitable for nebulisation.